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Psychology of Human Growth and Development
cognitive development part 2
Psychosocial development
Development of emotions
Language development
Cognitive development part 1
Perceptual development part 2
Development of attachment
Nature versus nature
Introduction to developmental theories
Prenatal development and chromosomal abnormalities
Prenatal development and teratogens
Brain development
Motor development
Physical growth
Perceptual development

Lecture 4


Prenatal development and chromosomal abnormalities



Critical periods of development


      The most dangerous time for an unborn baby is the embryonic period ( two weeks to three months fetal age) because this is when all of the basic organ systems are forming.


      After the embryonic period, the unborn baby grows and matures, but he has most of his basic biological equipment by this time.


Stages of prenatal development


      an embryo – during the first two months.


      a fetus- During the second trimester.


      a baby - During the third trimester,


The embryo has three layers from which all body organs develop.


Early formation of three layers of cells:


(1) the ectoderm, from which sense organs and nervous system will develop


 (2) the mesoderm, from which circulatory, skeletal and muscular systems will develop


(3) the endoderm, from which digestive and some glandular systems will develop.


Genetic Disorders


What are chromosomes?


Chromosomes are tiny string-like structures in cells of the body. They contain the estimated 20,000 to 25,000 human gene pairs that determine traits like eye and hair color, as well as direct the growth and development of every part of our physical and biochemical systems.


Each person normally has 23 pairs of chromosomes, or 46 in all. We normally inherit one chromosome per pair from our mother and one from our father.


X-linked Recessive trait




Hemophilia A is a hereditary blood coagulation (clotting) disorder. It is caused by a deficient activity of plasma protein factor VIII, which affects the clotting property of blood.



      Muscular dystrophy


An inherited disorder characterized by slowly progressive muscle weakness of the legs and pelvis.


The group of diseases called muscular dystrophies includes many inherited disorders such as: Becker's muscular dystrophy


      Diabetes Mellitus


Body’s inability to metabolize carbohydrates and maintain proper glucose levels


 Recessive Allele


      .Phenylketonuria (PKU)


A rare hereditary condition in which the amino acid phenylalanine is not properly metabolized; individuals with PKU have a deficient enzyme required for the metabolism of the amino acid phenylalanine.


      Cystic Fibrosis


An inherited disease that affects the respiratory and digestive systems. Cystic fibrosis affects the mucus and sweat glands of the body and is caused by a defective gene. Thick mucus is formed in the breathing passages in the lungs and this predisposes the person to chronic lung infections. Many pancreatic enzymes involved in the breakdown and absorption of fats in the intestine are absent, causing malabsorption (inadequate absorption of nutrients from the intestinal tract) and malnutrition.


Two Recessive Alleles in combination


      Sickle cell anemia


An inherited, chronic disease in which the red blood cells, normally disc-shaped, become crescent shaped. As a result, they function abnormally and break down, causing recurrent painful episodes.


Chromosomal abnormalities


      Down syndrome


Down syndrome, in which a baby is born with an extra chromosome 21,



Sex Chromosomal abnormalities


      Turner’s syndrome (XO)


A sex chromosome abnormality: Girls with Turner syndrome have only one X chromosome, instead of the normal two.


      Triple X (XXX)


A sex chromosome abnormality: Girls with Triple X have only one extra X chromosome, instead of the normal two.



      Klinefelter’s syndrome (XXY)


males with Klinefelter syndrome have one extra copy of the X chromosome in each cell. Klinefelter syndrome is caused by the presence of one or more extra copies of the X chromosome in a male's cells. Extra copies of genes on the X chromosome interfere with male sexual development, preventing the testicles from functioning normally and reducing the levels of testosterone.


      XYY Syndrome


chromosomal abnormality; extra Y


      Fragile X


A change or mutation in a gene on the X chromosome causes the fragile X syndrome. the gene responsible for fragile X syndrome is called the FMR1.